The present inventions refers to a method for printing an optical element comprising the steps of ejecting at least one droplet of printing material towards a substrate in a first step and curing the droplet deposited on the substrate in a second step.
It is well known from the applicant's prior art document WO 2010/091 888 A1 to print three-dimensional structures, in particular optical elements, by means of droplet-on-demand inkjet technologies. A movable print head is used for depositing single droplets of a transparent printing ink a certain positions onto a substrate. The print head is provided with UV light sources for curing the deposited droplets by UV irradiation. A three-dimensional optical element is built up by a plurality of deposited and cured droplets arranged at least partially one above the other and one beside the other.
Usually, a polymer based printing ink is used as curable printing ink for printing the three dimensional structures. A disadvantage of this purpose is that the heat stability of the three dimensional structures is comparatively low, so that the three dimensional structures are not suitable as optics for those light sources which generate much heat energy. There is a danger that the optic is melted through the heat.